OVH suggested me to change my IP “country” but the result was identical.
So it seems it’s the whole set of IPs from OVH that may have been blocked (best theory so far) but without any confirmation from twitter, there is no way to be sure of what going on.
But @PictaNews test seems to prove without any doubt that the issue is related to OVH servers.
However, a word from Twitter to tell us what’s really going on would really be appreciated !